1. Field of the Invention
The present invention relates to a heliostat. In more particular, the present invention relates to a light-collecting heliostat using flat mirrors, which does not only reflect the sunlight, but also concentrates the sunlight on one area at a high temperature, so that the concentrated sunlight can be used as a heat source of a solar thermal power plant.
Especially, the present invention relates to a heliostat using flat mirrors, in which the lights, which are reflected from the heliostat having a plurality of low-price flat mirrors arranged thereon for the reflection of the sunlight, represent one uniform temperature distribution while providing high-temperature light-collecting focal areas.
2. Description of the Related Art
Many power generators using natural power have been developed according to the depletion of fossil fuel. One of the power generators uses solar heat. Among the power generators using solar heat, there are solar thermal power plants. The solar thermal power plants are classified into a dish-type solar thermal power plant using a reflective plate and a tower-type solar thermal power plant using a heliostat.
Among them, the dish-type solar thermal power plant includes a dish-type reflective plate. In the case of the dish-type reflective plate, mirrors must be installed in such a manner that focal areas of the mirrors are concentrated on one area in order to concentrate lights from the mirrors on the one area. Accordingly, there are many difficulties when installing the mirrors.
In addition, since each mirror constituting the dish-type reflective plate must have a paraboloid in order to improve light collecting efficiency, there are many difficulties when manufacturing the mirrors.
Meanwhile, the tower-type solar thermal power plant uses lights reflected from the heliostat as a power source to drive a turbine.
In the tower-type solar thermal power plant, a reflective mirror of a heliostat to reflect lights requires high manufacturing cost, and is made of curved glass requiring a complex manufacturing process. In addition, for the purpose of high-temperature light collection, a great number of heliostats must be provided in such a manner that a plurality of scattered focal areas are overlapped with each other to obtain high temperature, and a light collecting unit having an area wider than a reflection area of the heliostat must be installed.
Further, in the tower-type solar thermal power plant, the lights reflected from the heliostat must be uniformly collected at a predetermined region of a heat collecting unit and irradiated onto the heat collecting unit in order to uniformly heat the entire portion of the light collecting unit, so that the power generation efficiency can be increased. However, if the curved glass is used as described above so that reflective mirrors having no uniform focal areas are provided in the manufacturing process, heat is concentrated onto only a specific region, so that the efficiency of the heat collecting unit not only be degraded, but the heat collecting unit can be easily aged due to the temperature difference.